1. Field of the Invention
The invention relates to the securing of building shafts, for example, light shafts, against forcible entry or passage. Such devices are installed, preferably retrofitted, in the light shafts of buildings that must be made especially secure, for example banks or prisons. The requirements for such devices are, therefore, the following: they must be simple to install and their components must be well secured against any kind of burglary tool.
2. Description of the Prior Art
DE OS 2 932 205 teaches a device in which the anchoring member of the blocking bars is formed by a box-frame member which is attached to the wall of the light shaft with dowels and which has several passages for receiving the ends of the blocking bars. The blocking bars are formed from round pipes inside which resides an equally round security rod which is intended to rotate when the blocking bar is being sawed in order to prevent the further advance of the saw. However, in order to make possible the installation, especially the retro-fitting of this device in an existing light shaft, the box-profile member must be attached at points lying between the recesses or passages that receive the individual blocking bars. To permit the subsequent tightening of the attachment bolts in these regions between the blocking bars, openings must be made in the box profile member and these must be covered with caps after the installation.
This known device offers a low level of security against forcing because suitable bending and burglary tools can so deform the blocking bars that the internal security rod is jammed and can no longer rotate. In addition, this device has the substantial disadvantage that the attachment bolts of the box profile member can be very easily exposed, even if the inside of the box frame member has been filled with concrete.